Oral tolerance is the ability of an antigen which is fed to decrease the subsequent systemic immune response to that antigen. The phenomenom has been described in both animals and in humans and is likely an important feature of the mucosal immune system for downregulating the immune response to innocuous antigens encountered in the gut lumen, some of which are absorbed in antigenically intact form. The presumed defect underlying Crohn's disease might be understood as a propensity for that individual to become immunized rather than tolerized to antigens encountered by the gut mucosa, possibly including dietary antigens. The proposed study seeks to determine whether individuals with Crohn's disease have an altered ability to achieve oral tolerization by measuring the specific immune responses to a soluble protein being eaten for the first time. To date, 34 patients out of an anticipated 126 patients have been enrolled. Data analysis will be done following completion by the protocol.